The use of fixtures for location and guidance of a drill bit to drill holes in a workpiece, such as a piece of wood, for pocket joints is well known. A pocket hole is one that is made at an angle in a piece of wood and a wood screw is inserted into the hole to join the workpiece to another wood piece. The screw is recessed in the pocket hole and is not exposed.
U.S. Pat. No. 6,254,320, which owned by the assignee of the subject application and the disclosure of which is incorporated herein by reference, discloses an improved and relatively simple fixture for making pocket holes in a workpiece. In accordance with the invention of that patent, the fixture is a U-shaped extrusion one leg of which is a guide leg against whose interior the surface of the workpiece in which a pocket hole to be drilled rests. The guide leg has angled channels to accept and guide a drill bit. The fixture leg opposite to the guide leg has a threaded hole through which passes a screw clamp and a base leg connects the guide and clamp legs to complete the U.
In the use of the fixture of the patent, the narrow edge of the workpiece rests on the interior of the base leg and the face surface in which the pocket hole is to be drilled is clamped against the interior surface of the guide leg by adjusting the threaded clamp to engage the opposite workpiece face. The distance between the base leg interior and drill bit guide channel exit sets the point on the workpiece at which the pocket hole is drilled. The clamp holds the workpiece securely against the guide leg while the drill bit is advanced through the angled guide channel to make an angled pocket hole in the workpiece.
The fixture of the patent is simple in construction and efficient in operation permitting precise drilling of a pocket hole in a workpiece. However, it has a limitation in that its use is substantially limited to a workpiece of one thickness which is basically determined by the distance between the exit of the guide channel for the drill bit and the upper surface of the base leg on which the workpiece narrow edge rests. Accordingly, it would be advantageous to be able to increase the functionality of a fixture of this type to be able to drill pocket holes in workpieces of different thicknesses.